1. Field of the Invention
This invention relates to a photovoltaic power generation device, more particularly relates to a photovoltaic power generation device for protecting a power inverter from an overvoltage.
2. Description of Prior Art
A solar cell device for generating photovoltaic power, which is located outside, has been paid attention as a promising way for solving the global environmental problems. A photovoltaic power generation system, in which a solar cell device arranged on a roof or the like generates power and covers the power consumed during the daytime, has been developed.
In this system, power outputted from the solar cell device is a direct current. Therefore, the power is inverted from the direct current outputted from the solar cell device into an alternate current by a power inverter before use.
The above power inverter does not start immediately after obtaining power generated in the solar cell device, but starts after checking output from the solar cell device for a predetermined time. It is because that noise may be generated in the output power when the power inverter starts under an unstable condition of power generation by the solar cell device such as at dawn of day.
As described above, since a conventional power inverter does not start until the power generated in the solar cell device is stabilized for a predetermined time, an open voltage increases. Particularly, in an early morning of winter, an open voltage becomes large. As a result, a power inverter with a larger withstand voltage than an operating voltage is required, and it causes an increase in cost and a deterioration in operation efficiency at a normal operating voltage.